1. Field of the Invention
The invention relates to a device for preventing re-use of a container for supplying ink to an ink printing head.
Such ink printing heads are used both in typical office printers and in small high-speed printers. The latter are components of modern machines for printing addresses or for product labeling and will soon also be part of machines for applying postage to mail.
The function of the printing heads should be assured in such a way that if at all possible no missing ink dots will occur. That is important not only for the sake of the printed image quality in general but also and in particular for security-relevant printed image data, such as the monetary value, the date and the serial number of the machine in the case of postage printing. If missing ink dots and damage to the printing head are to be prevented, among other requirements the supply of the proper ink for the ink printing head must be absolutely assured to be as free of bubbles as possible.
It is conventional (see German Patent DE 27 09 730 C2) for the ink connecting line from the ink printing head to the container for the ink supply, which is referred to below as the fresh ink container, to be docked on the ink container through a hollow needle. The ink container is provided with a rubber-elastic closure that is pierced by the hollow needle. That prevents both the invasion of air into the ink connecting line and an unintended escape of ink from the ink container. However, with that docking principle, it is possible for partly or entirely emptied fresh ink containers to be refilled with any arbitrary ink by unauthorized persons and inserted into the printer. That can cause failure or even damage to the ink printing head.
In order to provide reliable ink supply, it is important to detect when the ink runs out and to signal that occurrence in good time. An ink exhaustion detection device is known (see German Patent DE 27 28 283 C2) in which two electrodes pass all the way through the bottom of the fresh ink container, and a transition resistance between the electrodes is measured and evaluated. The electrodes are disposed in wells that are molded into the container bottom. The prerequisite for the use of that kind of ink exhaustion detection is the use of an electrically conductive ink.
2. Summary of the Invention
It is accordingly an object of the invention to provide a device for preventing re-use of a container for supplying ink, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which increases functional security. It is additionally an object of the invention to develop a device for preventing re-use that allows the use of only new fresh ink containers prescribed by the printer manufacturer and prevents the use of fresh ink containers that have already been in operation and then refilled, while preserving the initially described docking of the fresh ink container and an ink exhaustion detection through the use of electrodes disposed in the latter.
With the foregoing and other objects in view there is provided, in accordance with the invention, in an assembly having an ink printing head, an ink connecting line connected to the ink printing head, a container with a bottom and a rubber-elastic closure for supplying ink to the ink printing head, a hollow needle docking the ink connecting line on the container through the closure, and at least two electrodes fitted through the bottom of the container as part of an ink exhaustion detection, a device for preventing re-use of the container, comprising a cover device for at least one of the electrodes, the cover device tripping irreversibly upon initial insertion of the hollow needle.
In accordance with another feature of the invention, there is provided at least one annular bead surrounding and protruding past at least one of the electrodes.
In accordance with a further feature of the invention, the at least one bead is rubber-elastic.
In accordance with an added feature of the invention, the bottom of the container has a well molded therein with an edge, the at least one electrode is fitted into the well, and the edge of the well protrudes past the at least one electrode.
In accordance with an additional feature of the invention, the cover device includes a shaft, a rocker supported rotationally movably about the shaft, two bearing blocks for the shaft, a resilient detent hook for the rocker, and a compression spring biasing the rocker.
In accordance with a concomitant feature of the invention, the rocker has a first, short lever arm with an end and a protrusion on the end for locking on the detent hook, and the rocker has a second, long lever arm with a lateral tooth as a stop for the hollow needle and an end with a lining for covering the electrode or the bead.
Since a covering device for at least one of the electrodes can be tripped irreversibly once and for all through the use of the hollow needle for the ink docking, the exhaustion of the ink is signaled at all times for a fresh ink container once docked, although after the hollow needle has been pulled out, regardless of how much ink is still left in the device for preventing re-use.
A fresh ink container that has been undocked once and then redocked can accordingly no longer be used for the ink supply but instead can then be used, if at all, only for ink disposal, as a waste ink container.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for preventing re-use of a container for supplying ink, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.